diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index a7320d272b34..031f4611e0ff 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -370,15 +370,14 @@ enum libbpf_map_type { LIBBPF_MAP_KCONFIG, }; -static const char * const libbpf_type_to_btf_name[] = { - [LIBBPF_MAP_DATA] = DATA_SEC, - [LIBBPF_MAP_BSS] = BSS_SEC, - [LIBBPF_MAP_RODATA] = RODATA_SEC, - [LIBBPF_MAP_KCONFIG] = KCONFIG_SEC, -}; - struct bpf_map { char *name; + /* real_name is defined for special internal maps (.rodata*, + * .data*, .bss, .kconfig) and preserves their original ELF section + * name. This is important to be be able to find corresponding BTF + * DATASEC information. + */ + char *real_name; int fd; int sec_idx; size_t sec_offset; @@ -1429,17 +1428,55 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map) return map_sz; } -static char *internal_map_name(struct bpf_object *obj, - enum libbpf_map_type type) +static char *internal_map_name(struct bpf_object *obj, const char *real_name) { char map_name[BPF_OBJ_NAME_LEN], *p; - const char *sfx = libbpf_type_to_btf_name[type]; - int sfx_len = max((size_t)7, strlen(sfx)); - int pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1, - strlen(obj->name)); + int pfx_len, sfx_len = max((size_t)7, strlen(real_name)); + + /* This is one of the more confusing parts of libbpf for various + * reasons, some of which are historical. The original idea for naming + * internal names was to include as much of BPF object name prefix as + * possible, so that it can be distinguished from similar internal + * maps of a different BPF object. + * As an example, let's say we have bpf_object named 'my_object_name' + * and internal map corresponding to '.rodata' ELF section. The final + * map name advertised to user and to the kernel will be + * 'my_objec.rodata', taking first 8 characters of object name and + * entire 7 characters of '.rodata'. + * Somewhat confusingly, if internal map ELF section name is shorter + * than 7 characters, e.g., '.bss', we still reserve 7 characters + * for the suffix, even though we only have 4 actual characters, and + * resulting map will be called 'my_objec.bss', not even using all 15 + * characters allowed by the kernel. Oh well, at least the truncated + * object name is somewhat consistent in this case. But if the map + * name is '.kconfig', we'll still have entirety of '.kconfig' added + * (8 chars) and thus will be left with only first 7 characters of the + * object name ('my_obje'). Happy guessing, user, that the final map + * name will be "my_obje.kconfig". + * Now, with libbpf starting to support arbitrarily named .rodata.* + * and .data.* data sections, it's possible that ELF section name is + * longer than allowed 15 chars, so we now need to be careful to take + * only up to 15 first characters of ELF name, taking no BPF object + * name characters at all. So '.rodata.abracadabra' will result in + * '.rodata.abracad' kernel and user-visible name. + * We need to keep this convoluted logic intact for .data, .bss and + * .rodata maps, but for new custom .data.custom and .rodata.custom + * maps we use their ELF names as is, not prepending bpf_object name + * in front. We still need to truncate them to 15 characters for the + * kernel. Full name can be recovered for such maps by using DATASEC + * BTF type associated with such map's value type, though. + */ + if (sfx_len >= BPF_OBJ_NAME_LEN) + sfx_len = BPF_OBJ_NAME_LEN - 1; + + /* if there are two or more dots in map name, it's a custom dot map */ + if (strchr(real_name + 1, '.') != NULL) + pfx_len = 0; + else + pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1, strlen(obj->name)); snprintf(map_name, sizeof(map_name), "%.*s%.*s", pfx_len, obj->name, - sfx_len, libbpf_type_to_btf_name[type]); + sfx_len, real_name); /* sanitise map name to characters allowed by kernel */ for (p = map_name; *p && p < map_name + sizeof(map_name); p++) @@ -1451,7 +1488,7 @@ static char *internal_map_name(struct bpf_object *obj, static int bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, - int sec_idx, void *data, size_t data_sz) + const char *real_name, int sec_idx, void *data, size_t data_sz) { struct bpf_map_def *def; struct bpf_map *map; @@ -1464,9 +1501,11 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, map->libbpf_type = type; map->sec_idx = sec_idx; map->sec_offset = 0; - map->name = internal_map_name(obj, type); - if (!map->name) { - pr_warn("failed to alloc map name\n"); + map->real_name = strdup(real_name); + map->name = internal_map_name(obj, real_name); + if (!map->real_name || !map->name) { + zfree(&map->real_name); + zfree(&map->name); return -ENOMEM; } @@ -1489,6 +1528,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, map->mmaped = NULL; pr_warn("failed to alloc map '%s' content buffer: %d\n", map->name, err); + zfree(&map->real_name); zfree(&map->name); return err; } @@ -1503,6 +1543,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, static int bpf_object__init_global_data_maps(struct bpf_object *obj) { struct elf_sec_desc *sec_desc; + const char *sec_name; int err = 0, sec_idx; /* @@ -1513,21 +1554,24 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj) switch (sec_desc->sec_type) { case SEC_DATA: + sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx)); err = bpf_object__init_internal_map(obj, LIBBPF_MAP_DATA, - sec_idx, + sec_name, sec_idx, sec_desc->data->d_buf, sec_desc->data->d_size); break; case SEC_RODATA: obj->has_rodata = true; + sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx)); err = bpf_object__init_internal_map(obj, LIBBPF_MAP_RODATA, - sec_idx, + sec_name, sec_idx, sec_desc->data->d_buf, sec_desc->data->d_size); break; case SEC_BSS: + sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx)); err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS, - sec_idx, + sec_name, sec_idx, NULL, sec_desc->data->d_size); break; @@ -1831,7 +1875,7 @@ static int bpf_object__init_kconfig_map(struct bpf_object *obj) map_sz = last_ext->kcfg.data_off + last_ext->kcfg.sz; err = bpf_object__init_internal_map(obj, LIBBPF_MAP_KCONFIG, - obj->efile.symbols_shndx, + ".kconfig", obj->efile.symbols_shndx, NULL, map_sz); if (err) return err; @@ -1931,7 +1975,7 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict) map->name = strdup(map_name); if (!map->name) { - pr_warn("failed to alloc map name\n"); + pr_warn("map '%s': failed to alloc map name\n", map_name); return -ENOMEM; } pr_debug("map %d is \"%s\"\n", i, map->name); @@ -3216,11 +3260,13 @@ static int bpf_object__elf_collect(struct bpf_object *obj) err = bpf_object__add_programs(obj, data, name, idx); if (err) return err; - } else if (strcmp(name, DATA_SEC) == 0) { + } else if (strcmp(name, DATA_SEC) == 0 || + str_has_pfx(name, DATA_SEC ".")) { sec_desc->sec_type = SEC_DATA; sec_desc->shdr = sh; sec_desc->data = data; - } else if (strcmp(name, RODATA_SEC) == 0) { + } else if (strcmp(name, RODATA_SEC) == 0 || + str_has_pfx(name, RODATA_SEC ".")) { sec_desc->sec_type = SEC_RODATA; sec_desc->shdr = sh; sec_desc->data = data; @@ -4060,8 +4106,7 @@ static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map) * LLVM annotates global data differently in BTF, that is, * only as '.data', '.bss' or '.rodata'. */ - ret = btf__find_by_name(obj->btf, - libbpf_type_to_btf_name[map->libbpf_type]); + ret = btf__find_by_name(obj->btf, map->real_name); } if (ret < 0) return ret; @@ -7831,6 +7876,7 @@ static void bpf_map__destroy(struct bpf_map *map) } zfree(&map->name); + zfree(&map->real_name); zfree(&map->pin_path); if (map->fd >= 0) @@ -8755,9 +8801,30 @@ const struct bpf_map_def *bpf_map__def(const struct bpf_map *map) return map ? &map->def : libbpf_err_ptr(-EINVAL); } +static bool map_uses_real_name(const struct bpf_map *map) +{ + /* Since libbpf started to support custom .data.* and .rodata.* maps, + * their user-visible name differs from kernel-visible name. Users see + * such map's corresponding ELF section name as a map name. + * This check distinguishes .data/.rodata from .data.* and .rodata.* + * maps to know which name has to be returned to the user. + */ + if (map->libbpf_type == LIBBPF_MAP_DATA && strcmp(map->real_name, DATA_SEC) != 0) + return true; + if (map->libbpf_type == LIBBPF_MAP_RODATA && strcmp(map->real_name, RODATA_SEC) != 0) + return true; + return false; +} + const char *bpf_map__name(const struct bpf_map *map) { - return map ? map->name : NULL; + if (!map) + return NULL; + + if (map_uses_real_name(map)) + return map->real_name; + + return map->name; } enum bpf_map_type bpf_map__type(const struct bpf_map *map) @@ -8976,7 +9043,12 @@ bpf_object__find_map_by_name(const struct bpf_object *obj, const char *name) struct bpf_map *pos; bpf_object__for_each_map(pos, obj) { - if (pos->name && !strcmp(pos->name, name)) + if (map_uses_real_name(pos)) { + if (strcmp(pos->real_name, name) == 0) + return pos; + continue; + } + if (strcmp(pos->name, name) == 0) return pos; } return errno = ENOENT, NULL;